You might well owe your health — maybe even your life — to Henrietta Lacks. You probably never heard of her. Yet she contributed immeasurably to vaccines, drugs and other treatments for polio, influenza, hemophilia, Parkinson's disease, HIV and many kinds of cancer. She helped scientists develop in vitro fertilization and cloning, map the human genome and study the effects of radiation from atomic bombs and in outer space.

Science journalist Rebecca Skloot's riveting debut book, The Immortal Life of Henrietta Lacks, is the story of how a cell sample taken from a poor, black mother of five as she lay dying of cervical cancer in 1951 turned into one of the most versatile and widely used tools in modern medicine. It's also the story of Lacks herself and how the family she left behind has been affected by her strange journey. And it raises important questions about medical ethics, particularly who owns — and potentially profits from — the tissues and fluids that doctors take from patients every day.

The key to Lacks' "immortal life" is the tissue sample doctors at Johns Hopkins Hospital in Baltimore took from an unusually virulent tumor on her cervix. The sample wasn't a biopsy. They already knew a viciously metastasizing cancer was killing her; her autopsy revealed so many tumors it "looked as if the inside of the body was studded with pearls."

The sample (although Lacks didn't know it) was a research tool for the laboratory of George Gey, a "reckless visionary" intent on finding a way to create cultures of living human cells that would reproduce indefinitely. In 1951, human cells could be coaxed into reproducing in the lab, but they died out too quickly to allow extended research.

Gey was just one of many scientists trying to develop cell lines, but he was the one who happened to get Lacks' cells. Cultured like countless other samples in his lab, they grew spectacularly — and kept growing.

In those days before the complete monetization of research, Gey happily passed vials of the cells — dubbed HeLa after their donor — along to other scientists around the world. Skloot documents the many places they have traveled and uses they have been put to, and how ubiquitous they are still.

It's an amazing story. One expert estimates that if all the HeLa cells that descended from that tiny sample could be brought together, they would weigh 50 million metric tons.

More than 30 years after Lacks' death, a German virologist, Harald zur Hausen, used HeLa cells to discover human papilloma virus 18, the cause of Lacks' tumor — and her cells' immortality. He won the Nobel Prize for his discovery, which led to the HPV vaccine that can now help prevent cervical cancer.

Skloot tells much more than the scientific side of this story, though. She is just as interested in the narrative of Henrietta Lacks and her family. Born in 1920, Henrietta grew up in the tiny town of Clover, Va. Her family was descended from black slaves and white slave owners, and they had been working the same tobacco fields for generations. After her mother died when Henrietta was 4, she was raised by her grandfather. He took in other grandchildren, too, and at 20 Henrietta married one of them, her cousin David "Day" Lacks.

They left the farm for Baltimore, where he found factory work. The marriage wasn't happy, but she was a loving mother to her five children. When she died, she was only 31, her youngest child just over a year old.

The family knew nothing of HeLa cells — although Johns Hopkins doctors called them in repeatedly for blood samples to supplement their research — until an article about Henrietta was published in Rolling Stone in 1976, 25 years after her death.

Skloot recounts her struggle to overcome the family's anger and suspicion when she approached them for interviews. Not only were they furious at researchers and corporations that had grown rich by using their mother's cells while they lived in poverty; Henrietta's children also bore the scars left by the appallingly abusive girlfriend of Day's who took their mother's place.

Over the years she spent researching the book, Skloot became friends with Henrietta's daughter Deborah, whose quest to reveal her mother's story is far more personal. It's also fraught by such issues as Deborah's limited education (which makes it difficult for her to understand the scientific research), her precarious physical and emotional health, and her immersion in some of the Lacks family's far from scientific beliefs — one of Henrietta's cousins is sure her cancer was caused by voodoo.

But Deborah is as determined as Skloot is to tell her mother's story to the world, and their relationship becomes a driving force in this compelling book. Together, they also search for the truth about Henrietta's other daughter, Elsie. Epileptic and mentally impaired, Elsie was institutionalized at age 5 at the Crownsville State Hospital, then known as the Hospital for the Negro Insane. The conditions in which its inmates lived and the experiments performed on them — on living people, not cell samples — were beyond brutal.

That deeply chilling chapter of medical research serves to underline the ethical issues that surround Henrietta's story, such as informed consent, privacy and a patient's rights to her own body. Whether those uncountable HeLa cells are a miracle or a violation, Skloot tells their fascinating story at last with skill, insight and compassion.

Colette Bancroft can be reached at cbancroft@sptimes.com or (727) 893-8435. She blogs on Critics Circle at blogs.tampabay.com/arts.